The invention in this case relates in one aspect to a novel method of growing large polycrystalline bodies of volatile 2,6 and 3,5 compounds.
Another aspect of the invention relates to a novel method for the production of large monocrystal bodies of volatile 2, 6 and 3, 5 compounds.
According to the methods that have been previously employed, the growth of single crystals of 2,6 and 3,5 compounds from the melt has frequently been carried out by use of a quartz crucible. Such a procedure is described in Brau et al U.S. Pat. No. 3,849,205 and in Holton et al J. Crystal Growth 6 (1969) 97-100. A major disadvantage in the use of these methods lies in the use of the quartz ampul. The problems that result from the use of a quartz ampul is that the ampul can only be used for a single time and frequently contamination occurs from the quartz. Further it has been found difficult to obtain large size crystals of 2,6 and 3,5 compounds when quartz ampules are employed.
In order to avoid the use of quartz ampules the use of graphite crucibles in crystal growing techniques has been suggested.
Such use of graphite crucibles for the growth of a 2,6 and 3,5 compound crystals has been described in K. K. Dubenskiy et al Sov. J. Optical Technology 36(2): 118-121 Jan. 1969, by Kikuma et al J. Crystal Growth 41 (1977) 103-108; and in Kikuma et al, J. Crystal Growth 44 (1978) 467-472.
In these methods monocrystals of 2,6 compounds such as zinc selenide are formed from the melt frequently by use of the Bridgman technique. However, due to the large internal pressures developed during the process and the porous nature of graphite, the use of the graphite crucible necessitates the use of high external pressures ranging from about 20 to 1,000 or more atmospheres. As a result the use of expensive equipment is required and it is very difficult to produce large size crystals. In addition due to the use of the high pressures undesirable inclusions such as gas bubbles occur in the resultant crystals, and the energy consumption is very high.